Undergraduate Research in Engineering at Rice
George Wells, Junior Chemical and Environmental Engineering student
Determining How Post-placement Processes Impact Cap Function
with Dr. Mark WiesnerContaminated sediment beds in waterways can be remediated in a variety of ways. One of the simplest and most cost-effective tactics is in-situ capping, in which the contaminated layer is isolated from the surrounding environment by a layer of sediment. The challenge for environmental engineers is to determine which mixtures of sediments, and what depositional processes, optimize cap mechanical stability and chemical impermeability. My research over the summer of 2001 focused on determining how post-placement processes such as sediment consolidation and deposition impact cap function. Furthermore, the research attempted to clarify current sediment deposition models and to lay out a framework for a new model of cap placement that would aid in determining optimum cap sediment makeup and deposition methods based on the environment of the contaminated bed.
The sediment mixture we focused on contained varying fractions of sand and clay with particle sizes ranging from 1 micrometer to 1 millimeter. The fractions of each material involved and the interactions between the two fractions impacted the sedimentation behavior of the mixture and the corresponding deposit morphology. Shape affects and the cohesive properties of the fractions both needed to be considered in the sedimentation model. In turn, the deposition morphology created by the sedimentation and consolidation behavior of the sediment mixture determined the chemical transport characteristics and mechanical stability of the cap itself. Sedimentation and consolidation behavior and deposit morphology will be studied using custom designed sedimentation columns, impregnation equipment, and light and electron microscopy. Characterization of sediment mixture will be determined using coulter counter, zetameter, zetasizer, and photon correlation spectroscopy, which are contained in a sedimentation lab that we setup this summer. Chemical impermeability of deposition will be studied through diffusion experiments, and mechanical stability measurements will be taken using a flume setup.
Perhaps the most important part of my research experience was simply being a part of the research process. I entered the in-situ capping project just as it was getting started; as such, I was given the opportunity to be a part of the planning stages and preliminary pilot studies of a complex research project involving research groups from several different universities. In addition to gaining an incredible amount of knowledge on fluid mechanics, sedimentation models, environmental remediation technologies, and other subjects directly related to in-situ capping, I was exposed to experimental techniques and practices that, although very important to the university's function and to technological developments in general in our society, are relatively unknown to the majority of undergraduates.
Department of Civil and Environmental Engineering
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